Bicyclic 1,2,3-Triazolium Ionic Liquids as a novel ionic liquid based catalytic systems for the preparation of spirobenzo[f]pyrano[3,2-c]chromene derivatives under ultrasonic irradiation conditions

A novel ionic liquid, 2-butyl-4,5,6,7-tetrahydro-2H-[1,2,3]triazolo[1,5-a]pyridin-8-ium hydrogen sulfate, was synthesized and employed as an efficient catalyst in the high-yield synthesis of spiro compounds featuring the benzo[f]pyrano[3,2-c]chromene scaffold. Through a three-component reaction involving 1-hydroxy-3H-benzo[f]chromen-3-one, malononitrile, and 1-benzylindoline-2,3-dione in ethanol under reflux and ultrasonic irradiation, 10 distinct compounds were successfully obtained in excellent yields ranging from 86% to 97%. The products were characterized comprehensively by Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), and CHN analysis. Notably, the protocol offers an efficient, non-chromatographic method for separation and purification, ensuring high-yield productivity and operational simplicity, making it a highly advantageous approach for synthesizing spiro compounds.